A BMI >35 does not protect patients undergoing cardiac bypass surgery from red blood cell transfusion

Abstract

The effect of obesity on allogeneic intraoperative blood product transfusion in patients undergoing coronary artery bypass graft surgery (CABG) is poorly understood. We analyzed the influence of obesity on the risk of intraoperative red blood cell (RBC) transfusion among 45,200 consecutive non-reoperative CABG procedures from a multi-institutional perfusion database. A body mass index (BMI) in obese I category was associated with a 9.9% decrease in transfusion risk (p<0.05). Compared to patients with a normal BMI, obese I and obese III patients do not have any change in the relative risk of RBC transfusion. Overweight and mild obesity have a protective role in reducing intraoperative blood transfusion during cardiopulmonary bypass (CPB) surgery. However, logistic regression analysis showed that much of the observed reduction in transfusion rates for obese patients can be accounted for by other known confounds. The lack of a linear effect of increasing BMI on blood transfusion risk is a novel finding and warrants further investigation.

Implications of obesity in cardiac surgery: pattern of referral, physiopathology, complications, prognosis

“…Overweight and mild obesity have a protective role in reducing intraoperative blood transfusion during CPB surgery. Indeed, given the increased total blood volume and higher body surface area, these patients are less prone to the hemodilution caused by the priming volume of the CPB; this reduces the hemodilution-related extravascular lung water accumulation and blunts CPB-related coagulopathy (16). The abundant mediastinal fat and the compression of minor bleeding sites by the higher intrathoracic pressure secondary to mass loading further reduce bleeding risk (4).…”

Lean Flow: Optimizing Cardiopulmonary Bypass Equipment and Flow for Obese Patients—A Technique Article

“…Women have long been treated identically to men, despite differing physiological needs. In the wake of our initial right-sizing project, we proposed that the use of smaller CPB circuits on female patients could further improve outcomes while meeting their perfusion needs (26). In a recent publication, women with high BMIs were at higher, statistically significant, risk of RBC transfusion than On protocol is perfusionist compliance with right-sizing algorithm, off protocol is not complying.…”